He practiced law for only two years when he was awarded a contract (in partnership with his father) to construct the National Pike's road-bed between Brownsville and Hillsborough, Pennsylvania, which was completed in 1820.

Ewing never returned to the active practice of law, but instead engaged in a variety of business and agricultural pursuits.

He was a staunch supporter of the Union cause during the Civil War, and in 1862, at the age of 66, served as Captain of Company F of the 6th Pennsylvania Regiment of Militia, which was briefly called up and deployed to Chambersburg, Pennsylvania during Robert E. Lee's Maryland invasion that September.

He also and operated a small coal mine a few miles north of Washington Borough in an area known as the Meadowlands.

In addition to his work on the National Road, Ewing was also a superintendent of construction over a portion of the Washington-Pittsburgh Turnpike in the mid-1830s.